Conventionally, microfabrication using a photolithography technique has been carried out in the production of a semiconductor device. The microfabrication is a processing method in which a thin film of a photoresist composition is formed on a substrate to be processed, such as a silicon wafer, and irradiated with a ray of an active light, such as an ultraviolet light, through a mask pattern having a pattern for a semiconductor device, and subjected to development, and the substrate to be processed, such as a silicon wafer, is etched using the resultant photoresist pattern as a protective film (mask). In recent years, as the integration degree of the semiconductor device produced is being increased, an active light ray having a shorter wavelength is used, namely, the active light ray used for the processing has been changed from a KrF excimer laser (wavelength: 248 nm) to an ArF excimer laser (wavelength: 193 nm). In accordance with such a tendency, adverse effects of irregular reflection of an active light ray from the substrate or standing waves cause serious problems, and a method of forming a bottom anti-reflective coating (BARC) between the photoresist and the substrate to be processed as a resist lower-layer film having a role of preventing reflection of the light has been widely employed.
As an anti-reflective coating, an inorganic anti-reflective coating comprised of, for example, titanium, titanium dioxide, titanium nitride, chromium oxide, carbon, or α-silicon, and an organic anti-reflective coating comprised of a light absorbing substance and a high molecular-weight compound have been known. The former requires a facility for forming the film, such as a vacuum evaporation apparatus, a CVD apparatus, or a sputtering apparatus, whereas the latter advantageously requires no special facility, and a number of studies have been made on the organic anti-reflective coating.
Recently, as a photolithography technique of a generation next to the photolithography technique using an ArF excimer laser (wavelength: 193 nm), an ArF immersion lithography technique in which exposure through water is performed has been put into practical use. However, the photolithography technique using a light has limitations, and, as a new lithography technique following the ArF immersion lithography technique, an EUV lithography technique using an EUV light (wavelength: 13.5 nm) or an electron beam has attracted attention.
In a semiconductor device production step using EUV lithography, a substrate covered with an EUV resist is subjected to exposure by irradiation with an EUV light, followed by development, to form a resist pattern.
In a semiconductor device production step using electron beam lithography, a substrate covered with an electron beam resist is subjected to exposure by irradiation with an electron beam, followed by development, to form a resist pattern.
As a composition for forming a resist upper-layer film for EUV lithography, a novolak material containing a naphthalene ring has been disclosed (Patent Literature 1).
A composition for forming a photoresist upper-layer film, which contains a mixed solvent of a solvent having an ether structure and an alcohol solvent, has been disclosed (Patent Literature 2).
A composition for forming a photoresist upper-layer film, which contains a solvent having an ether structure, has been disclosed (Patent Literature 3).
A composition for forming a protective film for immersion exposure, which contains a solvent having a ketone solvent, has been disclosed (Patent Literature 4).
A resist protective film material comprising a high molecular-weight compound obtained by copolymerizing repeating units having a carboxyl group and/or a sulfonic group and repeating units comprising a hydrocarbon has been disclosed (Patent Literature 5).
A method for forming an EUV or electron beam resist pattern comprising a polymer having at least any of an aromatic group and an aromatic hetero group has been disclosed (Patent Literature 6).
As mentioned above, a variety of compositions for forming an EUV lithography upper-layer film have been disclosed. Important properties required for the EUV lithography upper-layer film are that the upper-layer film can transmit an EUV light and cut off the above-mentioned OOB (out of band) emission and further can maintain the barrier property for outgassing from the resist, making it possible to form an excellent resist pattern.
Further, in the situation in which the composition of the present invention is practically used (in the production of a semiconductor device), from the viewpoint of handling of the composition, it is important that the composition itself has excellent storage stability (that is, the composition suffers no change in the properties even after being stored for a long time) and that when the composition is used in forming a resist upper-layer film, a problem, such as an application defect, is not caused. This is a property similarly required for the electron beam resist upper-layer film.
A composition for forming a resist upper-layer film which satisfies all the above-mentioned properties has not yet been known.